DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 
59 
spatulate recurrent cartilage ( rc.c.), right and left; it is hollow on its outside, convex 
within, and hides the fore part of the short median vomer (v.). The whole septum 
( p.e.) is moderately thick, and has the roof ( al.sp., al.e.) cut away. Behind, the outline 
of the septum is arched, but there is no special crista galli. Further back, and 
below, the presphenoidal cartilage ( p.s .) passes into the basisphenoidal ( b.s.), which 
is ossified. The naso-palatine canal is rather deep, and is divided along the mid¬ 
line for some extent into two channels by the vomer (v.) About this time the small 
hinder lateral vomer appears right and left of the forks of the vomer : it was not 
noticed in this specimen. Part of the frontal, nasal, maxillary, palatine, and pterygoid 
are seen in this view. The small front paired vomers (see in the Unau, Plate 15, 
fig. 5, v.) are probably already fused with the palatine processes of the premaxillaries. 
A large tract of the other half of this vertical section (Plate 8, fig. 9), with the orbito¬ 
temporal wall-bones—frontal, parietal, and squamosal (f, p., sq.), partly drawn, shows, 
also, the inside of the nasal labyrinth, with the lower, nasal, middle, and upper turbinal 
folds ( i.tb. line wrong, n.tb., m.tb., u.tb.). The orbitosphenoid ( 0 . 5 .) has lost its front 
and hinder fastening bands (see Plate 15, fig. 5), but it is still much larger than the 
alisphenoid (above b.s.), its angles, from which the bands have been absorbed, are 
rounded, and the upper margin is concave. Less than the antero-inferior fourth of 
this tract is ossified, and this centre lies in front of the optic foramen (II.), which is 
bounded behind by a very narrow tract of cartilage, soon to be absorbed! The lesser 
alisphenoid, and also its base (b.s.), is quite ossified ; it is a roughish, thick bilobate 
wing of bone, the hinder narrow lobe being separated from the broad front part by 
a deepish notch, under which is a small foramen ; the notch is the beginning of the 
foramen ovale (V 3 .), not finished on its outer side (see the Unau, also Plate 15, fig. 5). 
The internal carotid artery enters in at the notch between the alisphenoid and its 
base, and the 1st and 2nd branches of the 5th nerve (V 1, 3 .), pass out of the sphenoidal 
fissure between the two “ alse; ” afterwards a bar of bone divides the passage for the 
second branch of the 5th nerve from the sphenoidal fissure, thus anticipating the 
human foramen rotundum,—a very inconstant passage in the Mammalia, generally. 
The solidity of the bones at this part is shown by a transverse section of the ali¬ 
sphenoid, basisphenoid, and pterygoid (Plate 13, fig. 11, al.s., b.s., p.g.). 
An inner vieiv of the double mandible instructively follows that already described 
in the Unau (Plate 9, figs. 8 and 9). Here the superficial “ramus” (fig. 8, d.), 
shows a great difference between the two types, as already described; but the 
endoskeletal or more archaic parts are not so much unlike; part of the difference here, 
namely, the lessening of Meckel’s cartilage ( mk ), and the ossification of the 
“ossicula,” is due to age. The splenio-coronoid region of the ramus has thrust 
Meckel’s cartilage down to the lower edge of the mandible, and bent it into 
a curiously sinuous rod. The basal rod ( b.mn .) is large and quite perfect yet. 
The mallear portion (ml.) has a less lobular head, and a more dilated manubrium 
(m.ml.) than in the other kind, for there is well seen, from the inner side, a consider- 
1 2 
